In an outside plant, optical fibers are protected inside splice closures, also known as joint closures. Spliced optical fibers are protected from environmental hazards such as moisture, water, dust, soil, high temperature, ultraviolet rays etc. For most of the typical applications, a Free breathing closure will serve the purpose. Free Breathing Closure is abbreviated as FBC.
FBCs provide the features and functions that are common with typical splice closure. FBC is an enclosure that prevents the intrusion of wind-driven rain, dust, and insects. However, FBCs permit the free exchange of air with the outside environment. This free exchange of air with outside environment gave its unique name, Free-Breathing Closure.
One of the disadvantage of FBC is that vapor condensation will form inside the closure. In the actual deployment field, it is necessary to provide proper drainage provisions to prevent the accumulation of water inside the closure.
FBCs are cheaper than Environmentally sealed closures. Since FBCs does not have provision to seal the inside enviromment of closure with the outside environement, they are easy to manufacture. The absence of elaborate environmental sealing systems provided in Environmentally Sealed Closures result in less costly closures and simplified installation procedures for Free Breathing Clsoures. Usually, deployment of FBCs in the OSP is restricted to aerial and ground-level applications where there is no risk of water immersion or exposure to chemicals.